AI The padlock on the service gate at Camden Town had rusted into a single orange knuckle. Someone had cut the chain beside it instead, and the links lay coiled on the step like a shed skin.
Quinn ducked under the tape. The stairwell smelled of wet brick and old electricity, and her torch caught tiles the colour of nicotine, a poster for a 1987 West End revival peeling off the wall in long tongues. Seventy-three steps down. She counted them without meaning to.
At the bottom, arc lamps turned the disused platform into a stage. Forensics moved through the glare in white suits, crouching and rising. Detective Sergeant Danny Voss stood at the platform's lip with his hands in his coat pockets and his breath clouding in front of him.
"Morning, guv. Or whatever it is down here. My phone's given up."
"Who found him?"
"Engineer from TfL. Checking cable runs on the Northern line side, heard the generator hum through the wall and got curious." He jerked his chin toward the far end of the platform. "Came through the connecting passage, found our friend, lost his breakfast. Uniform's got him upstairs with a sweet tea."
"Generator?"
"Ours now. Theirs, the engineer reckons. Whoever cut the chain."
Quinn walked the platform's edge. The body lay on its side near a bench bolted to the wall, knees drawn up, one arm folded beneath the head like a sleeper on a night bus. Male, sixties, grey beard gone yellow at the mouth. A wool coat three sizes too big. Plastic carrier bags knotted around his ankles over the trouser legs.
"Rough sleeper," Voss said. "Found a way in, got his head down out of the rain, didn't wake up. Cold, drink, heart. Pick one. Pathologist'll tell us which."
"The chain was cut with bolt croppers."
"So he nicked some bolt croppers."
"And carried them down seventy-three steps and left them where?"
Voss opened his mouth, closed it. "Could be in one of the bags."
"Check."
He waved a white suit over. Quinn crouched beside the body, careful to keep her knees off the concrete. The man's hands were clean. Not scrubbed, but clean the way hands are when the owner has a sink and uses it. The nails were short, filed. On the left wrist, a pale band of skin where a watch had sat for years and sat no longer.
She glanced at her own wrist, at the leather strap worn soft as a glove, and back at his.
"His shoes."
"What about them?"
"Look at the soles."
Voss leaned in. Brown brogues, resoled at some point, the heels built up with a cobbler's rubber. The treads held no grit. No brick dust, no black tunnel grime, none of the pale powder that coated every surface on the platform and had already turned the forensic team's boot covers grey to the ankle.
"He walked down here," Quinn said, "through thirty years of dirt, and came out the other side with his soles clean."
"He cleaned them."
"With what? There's no water down here. And why bother, if you're about to lie down on the floor?"
The white suit came back. "No croppers in the bags, ma'am. Tins of beans, a paperback, some socks. That's your lot."
Voss scratched the back of his neck. "All right. So someone else cut the chain. Kids, urban explorers, whoever. He followed them in afterwards."
"Then where are his footprints?"
Quinn stood and swept her torch across the platform. The arc lamps flattened everything, so she held the beam low, skimming it along the ground at an angle, and the dust leapt into relief: the crisscross of forensic boot covers, the scuffed trail from the stairwell where she and Voss had come in. Beyond that the powder lay unbroken.
Except it didn't. Not quite.
She walked the beam slowly outward. The dust formed a floor of soft grey felt, yes, but under it, running the length of the platform, lay faint rectangles. Paired, evenly spaced. Two feet apart, then eight feet, then two again. Dozens of them, in a double row, like the ghost of a picket fence.
"What am I looking at?" Voss asked.
"Table legs. Trestles." She traced the pattern with the light. "Stalls down both sides. An aisle through the middle."
"A car boot sale. In a sealed Tube station."
"Something that wanted to stay sealed."
She moved to the nearest set of marks and squatted. The rectangles hadn't been pressed into the dust. They'd been left by the absence of it: someone had laid a thin, fresh coat over the whole platform, and it had settled a hair thinner wherever the legs had stood a moment before. She pinched some between gloved fingers. Too fine. Too even. It didn't clump like the real stuff near the stairwell, which carried damp and grease and the grey bloom of mould. This ran through her fingers like flour.
"This isn't dirt," she said. "Someone brought it in and sifted it over the platform."
"Why would anyone do that?"
"To make it look like no one had been here."
Voss laughed, a short uneasy bark. "Guv, that's a lot of effort for a squat."
She didn't answer. Near the bench, half buried in the false dust, something caught the torchlight and threw it back green. Quinn brushed the powder aside with the edge of her pen.
A compass. Brass, small enough to hide in a fist, its casing furred with verdigris the colour of pond water. She lifted it on the pen's tip and turned it over under the lamp. Tiny marks crowded the face, circles and hooked lines etched so fine they looked like frost, and none of them resembled a single cardinal point.
"Bag that."
"Right away." Voss held out an evidence pouch, frowning. "Antique. Worth something, probably. Maybe that's our motive. Someone rolled him for his valuables, missed that."
"Took his watch and left the brass."
"Couldn't see it in the dark."
"They had a generator."
The needle swung as she lowered the compass into the pouch. Quinn stopped. She held the bag flat on her palm and waited for it to settle north, toward the stairwell and the high street and Parkway above them.
It pointed at the wall.
Not north. East, toward the curved end of the platform, where the tiles ran into the tunnel mouth and the lamps gave out. She took a step to the left. The needle held. Another step. It followed, a dog tracking a scent.
"Faulty," Voss said. "It's a hundred years old."
"Then it'd point at nothing. It's pointing at something."
She walked toward the tunnel mouth with the pouch held in front of her like a divining rod, and she felt foolish, and she kept walking. The needle trembled and steadied. The air changed as she went, the cold of the platform thinning, and when she reached the last run of tiles she pulled off one glove and laid her bare hand flat against the wall.
Warm. Warm the way a brick is warm an hour after the sun leaves it, down here where no sun had ever reached.
Everywhere else on the platform the tiles wore a crust of black soot and white saltpetre. Here, in a rough oval taller than a man, they gleamed. Cream glaze, the grout still white. Scrubbed, or never dirtied at all.
Three years ago, on a landing in a tower block in Deptford, the air had turned warm around her like this. Morris had gone up the last flight of stairs ahead of her. She had heard him say her name, once, conversational, the way he said it when he'd found a biscuit tin in a suspect's kitchen. When she reached the top the landing was empty and the wall behind it gleamed.
She took her hand away.
"Guv?"
"The coroner will find he didn't die here."
Voss came up beside her, pouch in hand, eyes on the clean tiles. "Based on what?"
"His shoes. He never walked in. Someone carried him and laid him down after they'd packed up their tables, and then they sifted the floor to cover the lot." She pointed back down the platform, the paired rectangles, the aisle. "Fifty stalls, maybe more. People buying and selling, down here, by lamplight. And they cleared out before dawn and left him behind."
"Why leave him at all? Why not take him with them?"
Quinn looked at the compass. The needle had not moved. It lay pinned toward the oval of clean tile as if the wall had swallowed a magnet.
"Because wherever they went," she said, "they couldn't take him through."